Increase local corrections to 10Hz in moving baseline application

IoT Modules GNSS Module
1

Hi,

I have a pair of LC29HEA dev board from quectel. The datahsset says the RTK is @10Hz. My application is direct moving baseline output for heading on a moving object.

I can’t find a way to increase local corrections at 10Hz. How can the module output 10Hz heading if the local corrections are @1Hz ?

2

Hi @mkergo35

For the LC29H(EA) module in a Moving Base configuration, it is normal and expected for the base station to output local corrections (RTCM) at 1Hz even when the rover provides a 10Hz heading output.

Here is the technical explanation and the configuration steps to ensure you are getting the desired performance:

1. How 10Hz Heading Works with 1Hz Corrections

In high-precision RTK systems, the rover does not require correction data to arrive at the same rate as its own position/heading calculations.

  • Rover Processing: The LC29H(EA) rover tracks satellite raw observations (carrier phase) at its internal update rate (10Hz).
  • Extrapolation: When the rover receives a 1Hz correction packet from the Moving Base, it applies those corrections to its current 10Hz observations. Between correction packets, the rover’s RTK engine uses internal algorithms to extrapolate the corrections, maintaining a high-rate RTK Fixed or RTK Float solution.
  • Heading Derivation: The heading output ($PQTMTAR) is derived from the baseline vector between the two antennas, calculated at the rover’s 10Hz rate.

2. Required Configuration for 10Hz Heading

To ensure your setup is correctly outputting heading at 10Hz, verify the following configurations:

  • Set the Fix Rate: Ensure the position fix interval is set to 100ms (which equals 10Hz).
    • Command: $PQTMCFGFIXRATE,W,100*5C . * Note: For this to take effect on the EA variant, you must save the configuration ($PQTMSAVEPAR ) and then manually reboot/restart the module.
  • Enable Heading Message ($PQTMTAR): Use the proprietary message rate command to ensure the heading information is output every fix.
    • Command: $PQTMCFGMSGRATE,W,PQTMTAR,1,1*09 .
    • The base station acts as the primary interface; it receives the heading calculated by the rover and outputs it to your MCU.

3. Bandwidth and Baud Rate Constraints

Operating at 10Hz significantly increases UART data volume.

  • Minimum Baud Rate: You must set your UART baud rate to at least 460800 bps to prevent data loss or buffer overflows that can occur when pushing 10Hz RTK data.
  • Default Rate: The LC29H(EA) defaults to 10Hz for RTK and 460800 bps for UART1.

Summary Checklist

  1. Do not try to increase local corrections: 1Hz RTCM from the Moving Base is sufficient for a 10Hz heading solution.
  2. Verify Fix Rate: Confirm it is 100ms using $PQTMCFGFIXRATE,R .
  3. Check Message Rate: Confirm $PQTMTAR is set to output every fix (Rate = 1).
  4. Hardware Reset: Ensure you have performed a hardware power cycle or a reset via the RESET_N pin after saving these settings.

Best Regards.